Based on the best-seller by Laura Hillenbrand (Seabiscuit), this ambitious film tells a story that would be outlandish except for the fact that it’s true.

When Louis Zamperini died earlier this year at age 97, he could look back on a personal history that included juvenile delinquency, a stint as an Olympic athlete, and WWII adventures as an Army Air Corp bombardier. Zamperini survived seven weeks drifting on the Pacific in a life raft, and two years as a prisoner of war of the Japanese, enduring hellish punishments above and beyond those routinely suffered by his fellow POWs.

That’s a lot of life to cram into a feature film — and the screenplay by Joel and Ethan Coen, William Nicholson and Richard LaGravenese already has drawn fire for what it has left out. More on that later.

Though Zamperini is played as a youth by C.J. Valleroy, the movie is owned by Brit actor Jack O’Connell, whose adult Louis quickly emerges as the one character with whom we identify. Other players come and go, but “Unbroken” is virtually a one-man show and O’Connell sinks into the role with almost documentary understatement.

Sumptuously mounted with some terrific action sequences — two bomber crashes plus those long weeks bobbing on a shark-filled sea — the film establishes early and maintains throughout the idea that after a difficult start, Louis was a man determined to survive and succeed.